This Battlefield 3 video Q&A features GameStar's interview with EA/DICE's Patrick Söderlund talking about Battlefield 3 (thanks GameSpy). One of the community questions they ask is about whether they plan to release mod tools with the game, to which Patrick says no: "Well as of now we're not going to make any modding tools, no." Here's his reply when asked why: "'Cause if you look at the Frostbite engine, and how complex it is, it's going to be very difficult for people to mod the game. Because of the nature of the set up of levels, the destruction, and all those things, it's quite tricky, so we think it's going to be too big of a challenge for people to make a mod."

Dev wrote on Jul 6, 2011, 20:12:It should be possible to make a level without cooking, since it the game resources are already in the files, and it shouldn't matter if you duplicate some stuff in the map files.

Those assets would likely have to be uncooked/raw in order to use them in making a map initially, that alone is already probably beyond the filesize they're willing to distribute for mod tools.

Let's say for some reason they don't have to be uncooked, now you're stuck using only the archives common to all the maps. They patch and all custom maps would likely be broken.

Okay, so you're going to create all your own assets instead and cook them using the provided mod/map tools... Start working on your own game at this point.